Nitrogen and oxygen self-doped hierarchical porous carbon nanosheets derived from turmeric leaves for high-performance supercapacitor

It is a formidable challenge to develop efficient and low-cost nanostructured carbonaceous materials for electrochemical energy storage application. Herein, a hierarchical porous carbon nanosheet is successfully synthesized in a facile manner from turmeric leaves by a two-step chemical activation strategy using KOH activator. The biomass-derived interconnected two-dimensional (2D) carbon framework prepared at 900 degrees C presents high selfdoped N (11.42 at%) and O contents (7.77 at%) together with specific surface area and pore volume of 541 m2/g and 0.47 cm3 g-1, respectively. Consequently, the resultant electroactive functional material shows a specific capacitance of 389 and 310 F/g at a current density of 1 A/g in acidic and neutral electrolytes, respectively. Additionally, an assembled symmetric supercapacitor device in Na2SO4 electrolyte delivers good capacitance retention of 90 % after 5000 consecutive charge-discharge cycles along with high specific energy (39.44 Wh kg- 1 at specific power of 0.49 kW kg- 1). This work provides a cost-effective, eco-friendly and sustainable outlook to prepare high-valued porous carbons from reliable biomass sources for high-performance supercapacitor application.